The present invention relates to intraocular lenses (IOLs) and a method for making and using the same. More particularly, the present invention relates to IOLs designed primarily for refractive correction in phakic eyes where the eye""s natural lens remains intact.
Visual acuity deficiencies such as myopia (nearsightedness), hyperopia (farsightedness), presbyopia (age-related farsightedness), aphakia (absence of the crystalline lens of the eye) and astigmatism (irregular conformation of the cornea of the eye) are typically corrected through the use of refractive lenses such as spectacles or contact lenses. Although these types of lenses are effective in correcting a wearer""s eyesight, many wearers consider the lenses inconvenient. The lenses must be located, worn at certain times, removed periodically and may be lost or misplaced. The lenses may also be dangerous or cumbersome if the wearer participates in athletic activities or suffers an impact in an area near the eyes.
The use of surgically implanted anterior chamber IOLs as a permanent form of refractive correction has been gaining in popularity. IOL implants have been used for years in the anterior or posterior chamber of aphakic eyes as replacements for diseased natural crystalline lenses that have been surgically removed from the eyes. Many different IOL designs have been developed over past years and proven successful for use in aphakic eyes. The successful IOL designs to date primarily include an optic portion with supports therefor, called haptics, connected to and surrounding at least part of the optic portion. The haptic portions of an IOL are designed to support the optic portion of the IOL in the lens capsule, anterior chamber or posterior chamber of an eye once implanted.
Commercially successful IOLs have been made from a variety of biocompatible materials, ranging from more rigid materials such as polymethylmethacrylate (PMMA) to softer, more flexible materials capable of being folded or compressed such as silicones, certain acrylics, and hydrogels. Haptic portions of the IOLs have been formed separately from the optic portion and later connected thereto through processes such as heat, physical staking and/or chemical bonding. Haptics have also been formed as an integral part of the optic portion in what is commonly referred to as xe2x80x9csingle-piecexe2x80x9d IOLs.
Softer, more flexible IOLs have gained in popularity in recent years due to their ability to be compressed, folded, rolled or otherwise deformed. Such softer IOLs may be deformed prior to insertion thereof through an incision in the cornea of an eye. Following insertion of the IOL in an eye, the IOL returns to its original pre-deformed shape due to the memory characteristics of the soft material. Softer, more flexible IOLs as just described may be implanted into an eye through an incision that is much smaller, i.e., 2.8 to 3.2 mm, than that necessary for more rigid IOLs, i.e., 4.8 to 6.0 mm. A larger incision is necessary for more rigid IOLs because the lens must be inserted through an incision in the cornea slightly larger than that of the diameter of the inflexible IOL optic portion. Accordingly, more rigid IOLs have become less popular in the market since larger incisions have been found to be associated with an increased incidence of postoperative complications, such as induced astigmatism.
After IOL implantation, both softer and more rigid IOLs are subject to compressive forces exerted on the outer edges thereof, which typically occur when an individual squints or rubs the eye. This is particularly true of IOLs implanted in the anterior chamber of an eye. Such compressive forces on an IOL may result in tissue damage, decentration of the IOL and/or distortion of the visual image. Compressive forces exerted on an IOL also tend to cause movement of the IOL haptics and axial displacement of the IOL along the optical axis of an eye. Haptic movement and broad haptic contact in the angle of the anterior chamber of an eye has the potential to cause damage to delicate structures within the eye such as the peripheral corneal endothelium, the trabecular meshwork and/or the iris. Movement of an IOL along the optical axis of an eye has the potential to cause the IOL to contact and damage the delicate corneal endothelial cell layer of the eye. Also, IOLs of current designs, whether formed of either softer or more rigid materials, tend to deflect along the optical axis of an eye when the haptics are compressed. IOL manufacturers provide a wide range of IOL sizes to more precisely fit IOLs to each particular patient""s eye size. Providing a wide range of IOL sizes is an attempt to minimize the potential for haptic compression and the associated axial displacement of the IOL optic along the optical axis of an eye.
Because of the noted shortcomings of current IOL designs, there is a need for IOLs designed to minimize haptic contact and movement in the angle of the anterior chamber and to minimized axial displacement of the IOL optic portion along the optical axis of the eye when compressive forces are exerted against the outer edges thereof. By lessening an IOL""s optic and haptic movement, more certain refractive correction may be achieved and the risk of delicate tissue damage may be reduced.
An anterior chamber intraocular lens (IOL) made in accordance with the present invention has an optic portion with an outer peripheral edge and two or more but preferably three or four haptic elements for supporting the optic portion in a patient""s eye. Three or four haptic elements are preferred in the present invention to provide a balance between IOL stability and minimized haptic contact in the angle of the anterior chamber. A lens having three haptic elements is balanced or stabilized by having two spaced haptic elements formed on one edge of the optic and the third haptic element formed on an opposite edge of the optic or alternatively stabilized by having each of the three haptic elements spaced on the edge of the optic with an equal distance therebetween. A lens having four haptic elements is balanced or stabilized by having two spaced haptic elements formed on one edge of the optic and two spaced haptic elements formed on an opposite edge of the optic or alternatively stabilized by having each of the four haptic elements spaced on the edge of the optic with an equal distance therebetween. Each of the haptic elements is of like form to achieve a rotational effect for ease of implantation, turning and centering of the IOL and to achieve the desired rotation and flexure functions described in greater detail below. Each of the haptic elements also has an inner portion and an outer portion with the inner portion being connected to the outer peripheral edge of the optic portion. Each haptic element includes a contact button or small knob on the outer portion thereof. The contact buttons are designed to minimally engage inner surfaces of a patient""s eye.
Each haptic element also has a central portion that extends between the contact button and the inner portion. Within this central portion, each haptic element is designed to have greater resistance to bending in a plane generally parallel to the optical axis of an eye than in a plane generally perpendicular to the optical axis of an eye. By providing haptic elements with this type of flexibility characteristic, the present IOL fits eyes of varying sizes. The flexibility characteristic of the subject haptic elements relative to the optic portion eliminates unacceptable axial displacement of the optic portion along the optical axis of an eye when compressive forces are exerted against the haptic elements of the IOL. In the present IOL, compressive forces are not dispersed through axial displacement of the optic portion, but rather through planar, rotational movement of the optic portion.
Accordingly, it is an object of the present invention to provide intraocular lenses for use in phakic eyes.
Another object of the present invention is to provide intraocular lenses for use in phakic eyes, which fit a variety of eye sizes.
Another object of the present invention is to provide intraocular lenses for use in phakic eyes, which minimize axial displacement of the optic portions of the lenses along the optical axis of the eyes.
Another object of the present invention is to provide intraocular lenses that allow for increased ease of implantation, turning and centering of the same.
Another object of the present invention is to provide intraocular lenses for use in phakic eyes, which minimize damage to tissues in the interior of the eyes.
Still another object of the present invention is to provide intraocular lenses, which are resistant to decentration within the eyes.
These and other objectives and advantages of the present invention, some of which are specifically described and others that are not, will become apparent from the detailed description, drawings and claims that follow, wherein like features are designated by like numerals.